In my part of the world (Australia) a vacuum pump for gel blotting
(generating a vacuum of around 40cm H2O) costs about $1500.00
(US$1200.00) so I decided to make one for myself.
It cost around $70.00, is very easy to make and has its own vacuum
gauge. The easiest way to describe it is by diagram, so if you want a
copy just email me at R.Passey at UNSW.edu.au and I'll send you one ASAP.
Cheers,
Robert Passey.